An Ames room is viewed with one eye through a pinhole such as to avoid any clues from stereopsis, and it is constructed so that from the front it appears to be an ordinary cubic-shaped room, with a back wall and two side walls parallel to each other and perpendicular to the horizontally level floor and ceiling. However, this is a trick of perspective and the true shape of the room is trapezoidal: the walls are slanted and the ceiling and floor are at an incline, and the right corner is much closer to the front-positioned observer than the left corner (or vice versa). (See overhead view diagram to the right)

As a result of the optical illusion, a person standing in one corner appears to the observer to be a giant, while a person standing in the other corner appears to be a dwarf. The illusion is so convincing that a person walking back and forth from the left corner to the right corner appears to grow or shrink.

Studies have shown that the illusion can be created without using walls and a ceiling; it is sufficient to create an apparent horizon (which in reality will not be horizontal) against an appropriate background, and the eye relies on the apparent relative height of an object above that horizon.

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Ames' original design also contained a groove that was positioned such that a ball in it appears to roll uphill, against gravity. Richard Gregory regards this apparent "anti-gravity" effect as more amazing than the apparent size changes, although today it is often not shown when an Ames room is exhibited.

He speculates that "magnetic hills" (also known as "gravity hills") can be explained by this principle. For a magic mountain in Ayrshire, Scotland (known as the Electric Brae), he found that a row of trees form a background similar to the setting of an Ames room, making the water in a creek appear to flow uphill.[1]

For Gregory, this observation raises particularly interesting questions about how different principles for understanding the world compete in our perception. The "anti-gravity effect" is a much stronger paradox than the "size change" effect, because it seems to negate the law of gravity which is a very fundamental feature of the world. It seems counter-intuitive that the expectation "rooms are rectangular" can override such a fundamental experience. In contrast, the apparent size change is not such a strong paradox, as we do have the experience that objects can change size to a certain degree (for example, people and animals can appear to become smaller or larger by crouching or stretching).

A type of selective perceptual distortion known as the Honi phenomenon causes some married persons to perceive less size distortion of the spouse than a stranger in an Ames room.

The effect was related to the strength of love, liking, and trust of the spouse being viewed. Women who were high positive in this area perceived strangers as being more distorted than their partners. Size judgements by men did not seem to be influenced by the strength of their feeling toward their spouse.[2]

Further study has concluded that the Honi phenomenon does not reliably exist as first thought, but may be explained as sex difference influencing perception, with women interpreting a larger reading as a more meaningful or valuable perception of things than men's.[3]

The Ames room principle has been used widely in TV and movie productions for special effects when it was necessary to show actors in giant size next to actors in small size. For example, production of the The Lord Of The Rings film trilogy used several Ames room sets in Shire sequences to make the heights of the diminutively-sized hobbits correct when standing next to the taller Gandalf.[4]

The 2010 HBO film Temple Grandin utilized an Ames room in the opening title sequence, and later figures in the actual story, where the title character, with high-functioning autism, intuitively devises the illusion in a scale model as a science project.

The 2012 music video "Scream" by Korean Hip-Hop/Pop band 2NE1 features an Ames room with two dancers changing positions to one side to another while CL, one of the band members sings and dances hiding the middle part of the room.

Ames rooms feature as a recurring motif in the short story 'The Object of the Attack' (1985) by JG Ballard.

Ames room illusion method is used by ANTO master in Maanada Mayilada - a South Indian TV reality shows

In the game Super Mario 64, the room containing the two paintings that lead to the level Tiny-Huge Island are placed at the end of two opposite hallways similar to an Ames room. When the player is standing at the center of the room, the two hallways appear to have both the same depth and equally sized paintings. As the player approaches them, however, it is revealed that one painting is massive in scale and the other is miniature, respectively.